Which of the following is a synthesis reaction?

2Na + 2H 2 O 2NaOH + H 2
2S + 3O 2 2SO 3
2H 2 O 2 2H 2 O + O 2
CaCl 2 + F 2 CaF 2 + Cl 2

2Na + 2H2O -> 2NaOH + H2